fix: update default subtitle background color

docs/subagents/agents/codex-subtitle-bg-20260220T054247Z-h9cu.md

@@ -0,0 +1,37 @@
+# Agent: codex-subtitle-bg-20260220T054247Z-h9cu
+
+- alias: codex-subtitle-bg
+- mission: Update default subtitle background color to requested RGBA value
+- status: completed
+- branch: main
+- started_at: 2026-02-20T05:42:54Z
+- heartbeat_minutes: 5
+
+## Current Work (newest first)
+
+- [2026-02-20T05:44:45Z] handoff: completed TASK-89; default subtitle background updated to `rgb(30, 32, 48, 0.88)` across config defaults, docs examples, and renderer fallback CSS.
+- [2026-02-20T05:44:45Z] test: `bun test src/config/config.test.ts` pass (33/33) after adding regression assertion for `config.subtitleStyle.backgroundColor`.
+- [2026-02-20T05:42:54Z] intent: apply requested default subtitle background color change, keep scope minimal, run targeted tests.
+- [2026-02-20T05:42:54Z] planned files: `src/config/definitions.ts`, related config tests if default snapshot/assertions exist, subagent bookkeeping files.
+- [2026-02-20T05:42:54Z] assumptions: user requested exact value string `rgb(30, 32, 48, 0.88)`; apply to default subtitle background.
+
+## Files Touched
+
+- `docs/subagents/INDEX.md`
+- `docs/subagents/collaboration.md`
+- `docs/subagents/agents/codex-subtitle-bg-20260220T054247Z-h9cu.md`
+- `backlog/tasks/task-89 - Update-default-subtitle-background-RGBA.md`
+- `src/config/config.test.ts`
+- `src/config/definitions.ts`
+- `config.example.jsonc`
+- `docs/public/config.example.jsonc`
+- `docs/configuration.md`
+- `src/renderer/style.css`
+
+## Open Questions / Blockers
+
+- none
+
+## Next Step
+
+- none